مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2646
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: I was behind the Messenger of Allah (ﷺ) and I saw the whiteness of his armpits when he was prostrating.
Musnad Ahmad 2662Saheeh because of corroborating evidence; this is a da'eef i